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Subject: Fwd: Re: [CAP] CAP Security Using Digital Signatures
Hi again, This is the third message in the series. Cheers, Rex >Date: Thu, 12 Mar 2009 08:59:23 -0400 >X-Google-Sender-Auth: 7dc6dac7072e0fae >From: matt hoffman <matthoffman@acm.org> >To: Art Botterell <acb@incident.com> >Cc: cap-list@lists.incident.com >Subject: Re: [CAP] CAP Security Using Digital Signatures >X-BeenThere: cap-list@lists.incident.com >List-Id: Common Alerting Protocol Public Discussion > <cap-list.lists.incident.com> >List-Unsubscribe: <http://lists.incident.com/mailman/options/cap-list>, > <mailto:cap-list-request@lists.incident.com?subject=unsubscribe> >List-Archive: <http://lists.incident.com/pipermail/cap-list> >List-Post: <mailto:cap-list@lists.incident.com> >List-Help: <mailto:cap-list-request@lists.incident.com?subject=help> >List-Subscribe: <http://lists.incident.com/mailman/listinfo/cap-list>, > <mailto:cap-list-request@lists.incident.com?subject=subscribe> >Sender: cap-list-bounces@lists.incident.com >X-Nonspam: Statistical 54% > >I did a proof-of-concept implementation of this on a previous DHS system. >Although, as you say, there was no way of verifying it with other providers >or consumers at the time.However, a couple of points that I recall: > >a.) The document mentions that the signature element can be a child of >"alert", but unless I'm mistaken it is not specified in the schema. So >messages containing signatures fail schema validation ... I had to >explicitly add it to the schema. > >b.) The signatures are delicate, and tricky: >http://www.cs.auckland.ac.nz/~pgut001/pubs/xmlsec.txt > >Unfortunately I no longer have access to that code, but I'd be happy to help >others if they're looking into it. > > >- matt > >On Wed, Mar 11, 2009 at 11:20 PM, Art Botterell <acb@incident.com> wrote: > >> Friends - >> >> We're moving rapidly toward an important threshold in CAP implementations. >> So far, most CAP-based systems have been self-contained, single >> vendor/implementer arrangements. But soon we're going to need to "federate" >> CAP traffic among multiple interoperable systems. And that has important >> implications for security. >> >> Most current systems use a trusted-link/trusted-host mode based on >> encrypted network links and password access control at a central server. >> That's a familiar Web 1.0 approach and it works fine for "single-hop" >> implementations. But it has a major drawback: As soon as messages are >> forwarded from one server to another, a security compromise anywhere can >> compromise the authentication and integrity of all CAP messages downstream. >> >> The alternative, of course, is to apply digital signatures to CAP messages >> at their origin, and to verify them at receiving points. That way, it >> doesn't matter if the links or intervening nodes are secure or not; any >> recipient can verify independently that the message is a) from who it says >> it's from, and b) hasn't been modified in transit. >> >> There's a standard way of doing this for XML, as cited in the CAP >> Specification: >> >> >3.3.2.1 Digital Signatures >> >The alert element of a CAP Alert Message MAY have an Enveloped Signature, >> as described by XML Signature and >> >Syntax Processing [XMLSIG]. Other XML signature mechanisms MUST NOT be >> used in CAP Alert Messages. Processors >> >MUST NOT reject a CAP Alert Message containing such a signature simply >> because they are not capable of verifying >> >it; they MUST continue processing and MAY inform the user of their failure >> to validate the signature. >> >> But I'm not aware of anyone that's implemented it yet... partly because it >> hasn't been necessary in stand-alone systems, and partly because it involves >> a type of programming a lot of folks haven't had occasion to explore yet. >> >> But ultimately, it's going to be essential for interoperability. So I'd be >> interested in hearing, has anyone implemented XMLSIG on CAP yet? And would >> anyone be interested in doing some interoperability experiments? The >> standard is there, the technology is there (in Java and a number of other > > languages) and I see the requirement bearing down on us quickly. >> >> What say? >> >> - Art >> >> >> _______________________________________________ >> This list is for public discussion of the Common Alerting Protocol. This >> list is NOT part of the formal record of the OASIS Emergency Management TC. >> Comments for the OASIS record should be posted using the form at >> http://www.oasis-open.org/committees/comments/form.php?wg_abbrev=emergency >> CAP-list mailing list >> CAP-list@lists.incident.com >> http://lists.incident.com/mailman/listinfo/cap-list >> >> This list is not for announcements, advertising or advocacy of any >> particular program or product other than the CAP itself. >> >-------------- next part -------------- >An HTML attachment was scrubbed... >URL: ><http://lists.incident.com/pipermail/cap-list/attachments/20090312/8bc9f488/attachment.html> >_______________________________________________ >This list is for public discussion of the Common Alerting Protocol. >This list is NOT part of the formal record of the OASIS Emergency >Management TC. Comments for the OASIS record should be posted using >the form at >http://www.oasis-open.org/committees/comments/form.php?wg_abbrev=emergency >CAP-list mailing list >CAP-list@lists.incident.com >http://lists.incident.com/mailman/listinfo/cap-list > >This list is not for announcements, advertising or advocacy of any >particular program or product other than the CAP itself. -- Rex Brooks President, CEO Starbourne Communications Design GeoAddress: 1361-A Addison Berkeley, CA 94702 Tel: 510-898-0670
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